title: Is 18F-FDG PET/CT useful for distinguishing between primary thyroid lymphoma and chronic thyroiditis?
abstract: OBJECTIVE
  This study aims to investigate the usefulness of (18)F-FDG PET/CT for distinguishing between primary thyroid lymphoma (PTL) and chronic thyroiditis.
  
  
  METHODS
  We retrospectively reviewed the data of 196 patients with diffuse (18)F-FDG uptake of the thyroid gland and enrolled patients who were diagnosed as having PTL or chronic thyroiditis based on the medical records, pathological findings, and laboratory data. The enrolled patients comprised 10 PTL patients (M/F = 4:6) and 51 chronic thyroiditis patients (M/F = 8:43). Images had been acquired on a PET/CT scanner at 100 minutes after intravenous injection of (18)F-FDG.
  
  
  RESULTS
  The PTL group consisted of 7 patients with diffuse large B-cell lymphoma (DLBCL) and 3 with mucosa-associated lymphoid tissue (MALT) lymphoma. The maximum standardized uptake value (SUV(max)) was significantly higher in the PTL group than that in the chronic thyroiditis group (25.3 ± 8.0 and 7.4 ± 3.2, P < 0.001). On the other hand, the CT density (Hounsfield unit: HU) was significantly lower in the PTL group than that in the chronic thyroiditis group (46.1 ± 7.0 HU and 62.1 ± 6.9 HU, P < 0.001). Within the PTL group, the SUV(max) was significantly higher in the cases of DLBCL than in those of MALT lymphoma (29.0 ± 6.4 and 16.7 ± 2.3, P = 0.017).
  
  
  CONCLUSIONS
  The SUV(max) was significantly higher and the CT density was significantly lower in PTL as compared with those in chronic thyroiditis. Thus, (18)F-FDG PET/CT may be useful for distinguishing between PTL and chronic thyroiditis.
authors.affiliation: Department of Diagnostic Radiology and Oncology, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo. nkdtmrad@tmd.ac.jp
authors.forename: Masashi
authors.initials: M
authors.lastname: Nakadate
authors.forename: Katsuya
authors.initials: K
authors.lastname: Yoshida
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ishii
authors.forename: Masayuki
authors.initials: M
authors.lastname: Koizumi
authors.forename: Naobumi
authors.initials: N
authors.lastname: Tochigi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Ryu
authors.forename: Tassei
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Isao
authors.initials: I
authors.lastname: Umehara
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shibuya
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008223:Lymphoma / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012372:ROC Curve; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000473:pathology; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging*; D013966:Thyroiditis / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18